For the sources of the latest version go to github, click on the Clone or Download button and select "Download ZIP".
There is also a prebuilt binary for Linux (generally a bit out of date with respect to the sources) in github here.
If you find a prebuilt binary elsewhere, -> will show you its version. The current version of the source code is here.
You can find the sources for this version in the sqliteman area on github. You should be able to build it. I do now have access to an MS Windows machine. I will try to build it as and when I have time, but it is not a high priority for me since I don't normally use MS Windows.
Downloadable sqliteman for MS Windows can be found on the various third party sites. You can not be sure what these packages contain. Everything is probably fine there but there is no content warranty of 3rd party packages and they are likely to be older versions.
It's highly probable you have an sqliteman binary package prepared for your distribution. However this has probably been built from old and no longer maintained sources at pvanek/sqliteman. It should be better to build from the sources in github here or use the latest built release from github here .
Unfortunately I have no access to any Mac machine. Sqliteman should compile and run on this platform. It may be provided by 3rd parties again, but you are probably better off building from the sources in github here if you can.
Some reports from users tell that it can be built on Solaris, Opensolaris, *BSD. It may be provided by 3rd parties again, but you are probably better off building from the sources in github here if you can.