I have used MG and it's is *fast*, open source and indexes images (although I have not tried this out). And the C code is written cleanly for it to be converted into a AOLServer module. The only issue I have had is that I have not been able to find how to get it to recognize wild-card queries (I was told by someone who was at MDS that it supports it). Plus it supports get scripts as a method of inputting data, quite similar to the INSO filter mechanism in intermedia.
See The RMIT MDS MG homepage
Cheers,
Hafeez
