I'm looking for a tool that will help with gathering and maintaining requirements (most probably use case specifications)
I have used Rational Requisite Pro in the past and found it was OK but no longer have access to it
Is there anything else I could use?
Haven't tried it but there is the aptly named Open Source Requirements Management Tool.
I'm nor sure if the feature set will be as rich as Requisite Pro since I never used Requisite Pro before but you could look at Redmine if you want an open source solution. I know you ask for open source but I will recommend fogbugz because its an excellent tracking tool.
I know of a list of requirements management tools, none of them seems to be OSS/free, though.
Several in the table seems to cover the same set of features as Requisite Pro.
Be aware that the table is made from information provided by the vendors.
After a quarter century of developing professional, enterprise grade software, I decided to write a free, web based SDLC tool that combines the best of what I have worked with in the past (e.g. Rose, Doors, SFEE) plus adding what I felt was missing. I call it Code Roller.
With Code Roller, you capture requirements as user stories, walk throughs, etc. From there, you can organize the requirements to build out a complete information architecture.
Code Roller lets you manage all phases of development and not just the requirements. There are plenty of automation tools that accelerate your crafting use cases from the analysis. More tools help you craft test plans and designs from the use cases. This relationship is maintained over time so you can always track back easily from defect to test plan to design to use case to requirement.