Why look at open source now? - PLN
..The open source model offers librarians the capability to create the software that we’ve always wanted—-standards compliant, interoperable, extensible and scalable software that does what we want it to do: help customers find information quickly, conveniently, no matter where that information resides..I will say choose open source because it gives you the freedom to use, change or distribute the way you want. Remember, Libraries are expected to stay much longer than the vendors. Vendors may not support a version which they sold you some time ago. Or they may go out of business. In that case all your work and investment goes waste. You may be forced to migrate to another version or another software. With Open Source, you know what it all contains. You may tweak it yourself or hire people to do so, but then it is always with you. You can make it to evolve for your library's evolving needs.
Also check out the following paper at E-LIS repository:
E-LIS - A Virtual Exhibition of Open Source Software for Libraries
..Open source software is quickly becoming a preferred solution, owing to the freedom to copy, modify and distribute it and the freedom from contracts, as well as for greater opportunities for interoperability with other applications..