Write and preview sequence charts with MscGen and its brethren. Shortcut:
*.msc) it supports
MsGenny -> MscGen/ Xù,
MscGen -> MsGennyand
Xù -> MsGenny
Mscgen Preview: Translatein the command palette.
This software is free software licensed under GPL-3.0. This means (a.o.) you can use it as part of other free software, but not as part of non free software.
Good catch. Let us know what about this package looks wrong to you, and we'll investigate right away.