Testitool is a .gz file which you can extract using WinZIP, WinRAR, etc.
When creating your shortlist take a good look at numbers of downloads/forum posts, etc to see how active the community is. There are loads of resources on evaluating open source software which you can find through Google. I think TestLink is probably the biggest community and from the survey results coming in at the moment is by far the most popular of the test mgt tools.
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