I have just found out that a client is looking at bug/issue management systems, with the ones they've mentioned being Axosoft, Track Studio and Projector. (All but the latter are easy to find online, I've not found Projector's website).
The client will be using them, I believe, to track maintenance and other issues on their site (ie not software bugs).
Are there any good FOSS alternatives I should suggest to them or should I stay out of their way? I suspect that none of the off-the-shelf packages will do what they want and a FOSS option would make it easier to modify, but the other suggestion of building something from scratch will probably be a big uphill struggle unless it turns out they have very simple needs.