Many glass catalogs are available on the internet in the AGF file format used by the ZEMAX lens design program, making this file format something of a de facto standard.
For example, the following vendors make their glass catalogs available online the AGF format:
Another place to find ZEMAX format glass catalogs is the ZEMAX file exchange, where you can find the Russian GOST catalog in AGF format as well as AGF files of glass properties created by users of ZEMAX.
To use an AGF file with LensForge, you just open the file with LensForge and drag the glasses you want into your lens design. LensForge is, in fact, an AGF file viewer, and will give you quite a bit of information when you open the AGF file.
The screen capture above shows how LensForge presents an AGF file. You can select any of the glasses in list at left and drag them into your lens design. You can also enter a string into the search box at upper left and that will restrict the list of glasses to those whose name contains the specified string.