Aseprite is not open source :(

[encukou]

The licence for Aseprite doesn't meet the Open Source Definition. It would be better described as “source available”.
I wish that was just pedantic labeling.

The licence does not allow re-distribution, which means that if the project switches to an unaffordable licence, it'll only be legal to run:

• existing copies, and
• apps compiled from source, if you personally obtained the code before the switch.

The point of open source is that if something bad happens, the community can “fork” the existing version and continue maintaining it (e.g. port it to a new OS or add a new feature, and freely share the improvement with others). Aseprite only allows modifications “for your own personal purpose or to propose a contribution”, and they can reject contributions.

IANAL.

[hatmix]

https://libresprite.github.io/#!/ is the actual opensource alternative