To run mbID you need at least:
There may be some questions about disk space but it is really simple. You need 3MB to install the entire script with images, dlls, icons, ... . The other diskspace is used for logging. The more users, the more diskspace you need.
20 MB should be enough for running mbID 1 month for 10 (active) users. So if you want to run mbID for 50 users in 6 months you may need 600MB free space. If you can't meet this requirement you can always open your /logs/ folder and erase all logs.
Below you can find the requirements the script is tested on.
The only other thing you need is a decent internet connection. You have to handle lots of data so the better your internet connection, the faster your server.