Before building anything, I graded the open-source options against a single job: enter tasks with blockers between them, see those blockers on a Gantt, and open one page every morning that says which unfinished task is holding up the rest. Every candidate below gets a clickable mock-up of that exact screen — invented data, no connection to any server.
Ordered by how close they get to the third line of the ask. All six are free and self-hostable; what separates them is scheduling honesty, weight, and what the first screen shows.
PHP project system with a real dashboard: to-dos, milestones and goals on one screen.
Its default screen is already a daily queue. Dependencies are unlimited and the timeline draws connector arrows — but “blocked” is a flag you set, and the queue sorts by date.
closest to the morning pageBoard, list, calendar and Gantt views over work items, with linked tasks and GitHub sync.
Blockers are first-class relations with a chip on the card and a connector in the Gantt. One container plus Postgres, SSO in the free build. Board-first landing, no scheduling maths.
best modern baseA text DSL plus a scheduler that resolves dependencies and emits static HTML reports.
Real dependency semantics and a computed critical path — the only tool here that knows what a one-day slip does to the launch date. Input is a text file, not a form.
the only one that computesPersonal-scale task manager: list, table, kanban and Gantt views in one Go binary.
Installs without a database server and is fast to capture into. The Gantt draws bars only — relations are stored but never rendered, and dates never propagate.
lightest to runClassical PMO suite: work packages, Gantt with predecessor/successor, boards, budgets.
Predecessor/successor with lag is free, and automatic scheduling mode pushes successors when a bar moves. No critical path (their FAQ says so), and My page ranks by priority, not by what a task unblocks.
most depth, most weightLinear-style work items, cycles and docs with a Gantt layout and blocking links.
Beautiful and popular, but the Gantt plots dates you typed: blocking links exist and nothing is scheduled from them. Heaviest stack of the six to keep alive.
prettiest, least mathsWritten down first, so every cell below can be checked against a rule rather than an impression. C3 and C4 are what separate these tools from each other.
| Constraint | Leantime | Kaneo | TaskJuggler | Vikunja | OpenProject CE | Plane CE |
|---|---|---|---|---|---|---|
| C1Enter a dependencyA task can be linked to another as blocker/blocked-by, finish-to-start, without a plugin or a paid tier. | ✓unlimited deps | ✓blocking + relates | ✓depends / precedes | ~blocking relations | ✓FS + lag, free | ✓blocking links |
| C2See it on the GanttThe chart draws an arrow from the blocking task's bar to the task it holds up. | ✓arrows | ✓arrows | ~static report | ✗bars only | ✓arrows, live | ~bars, links in panel |
| C3Dates that moveSlide a blocker and its successors follow. Without this the Gantt is a drawing of assumptions. | ✗no propagation | ~links kept, dates typed | ✓scheduler resolves | ✗no propagation | ~auto mode pushes successors | ✗no propagation |
| C4A blocker-first landing pageOne screen, opened daily, that orders work by what it unblocks — not by due date, priority or assignment. | ~dashboard by date | ~blocked-only filter | ✓critical path report | ~saved filter | ~My page by priority | ~saved views |
| C5Runs on this boxFits in 8 GB of RAM beside three existing apps, no seat fees, no third-party account. | ~php + mysql | ~docker + postgres | ✓a ruby gem | ✓one binary, sqlite | ~Rails + pg + memcached | ~4 containers + redis |
| C6Cheap to keep currentAdding or re-dating one task takes seconds, from the phone too, or the plan decays. | ✓fast capture | ✓fast capture | ✗edit text, rerun | ✓fast capture | ~forms, many fields | ~forms + cycles |
✓ met · ~ partially · ✗ not available in the free, self-hosted build. Versions and licences read from each project's releases on 31 Oct 2026.
Each mock-up is the screen that tool would put in front of you on day one, redrawn from its public documentation — same project, same invented dates, so the models can be compared rather than the paint.
PHP + MySQL, official Docker image. Around 500 MB RAM with a small database — comfortable here.
Mock-upleantime.html
Those two gaps are exactly what a 150-line generator fixes: read the API, sort open tasks by how many downstream tasks they hold, write one page.
App + Postgres via Docker Compose. Around 700 MB RAM.
Mock-upkaneo.html
Best pick if you want a modern tool to live in and are willing to generate the morning view.
A Ruby gem and one CLI. Zero daemons; the report is a file.
Mock-uptaskjuggler.html
Fits a plain-file habit — and this box already serves static pages. The model can be the source of truth while a nicer tool shows it.
One binary, around 150 MB RAM, a SQLite file to back up.
Mock-upvikunja.html
A good capture layer — but you would end up generating the visual dependency view yourself, at which point the built-in Gantt earns little.
Docker Compose: web + worker + Postgres + memcached. 2–4 GB RAM to be comfortable.
Mock-upopenproject.html
The right answer if you later need a real PMO process with other people. Overkill for one operator.
Web + space + worker + Postgres + Redis + object storage. Around 4 GB RAM.
Mock-upplane.html
Choose it for the Linear feel with a team; it buys you nothing on the dependency question.
None of these is bad software; each is wrong for this one job.
All six can store “A blocks B”. Only TaskJuggler computes what that means — slack, critical path, the launch date if you slip a day. The rest store the relation and let you type the dates, which makes their Gantt an illustration of your assumptions rather than a schedule.
The daily blocker page is the piece nobody has. Leantime gets closest by making a dashboard the home screen, and OpenProject's My page is a respectable assigned-work queue — but both order by date and priority. Neither answers “which task, finished today, unblocks the most downstream work?” That ordering is a five-line query over the dependency graph; products skip it because most teams assign work to people instead.
Which is the honest argument for a small build — not a whole system, one page. Capture, relations and the Gantt already exist, free.
blockers.html — served here next to the others.