The app is free.
Running it is not.
OpenAnstruk costs nothing to use and it is going to stay that way. There is no licence key, no seat count, no institution you have to belong to. If you are a student with a laptop and an assignment due, that is enough.
What it does cost is time and a small amount of money, and both come out of one person's evenings. A donation does not buy you anything the next person does not get. It buys the project more of the thing it is actually short of.
Where the money goes
- The domain, and the hosting that serves the app to everyone who opens it.
- Licences for the commercial software the solver is checked against. Verification is the expensive part of building an analysis tool, and it is not optional — a wrong number that looks right is worse than no tool at all.
- Reference codes and standards, which are not free to obtain and have to be re-bought as they are revised.
- Hours. Every feature in the app exists because an evening went into it instead of somewhere else.
Nothing here is a subscription and nothing recurs unless you set it up that way. If you would rather not send money, telling a colleague the tool exists is worth more than most donations.
Ways to support
Email works today. The rest are being set up and will appear here as they open — they are greyed out rather than hidden so you can see what is coming.
What open means here
Open tool. Open knowledge. Open access. That has been the promise since the beginning, and the third word is the one that matters most to whoever is opening the app right now.
The 2D application is open source under the MIT licence, permanently. You can read every line of the solver, check it, fork it, and run it yourself. The source is here.
The 3D application is not open source, and it is fairer to say so plainly than to let the name imply otherwise. Its source stays closed; its access does not. Structural analysis software is used by engineers rather than by developers, so publishing the source attracts almost no contributions — while the validation record that makes the numbers trustworthy means an outside change to the solver would cost more to re-anchor than to have written. That is the cost of open source without the benefit. Free to use is the part worth keeping, so that is the part being kept.