Gerber Merge Software preferably free open source

[TheOCDengineer]

Hi Everyone

New to the form. I am teaching an intro into circuits course at a university. The students have an option to put their final project on a PCB. I was able to get a sponsorship from custom circuit boards for them to make the boards for us, so shout to to them. I am teaching the students to use kicad as that is what i am familiar with and I am asking them to send me their gerber files approx 40 boards. I am wondering what is the best free gerber merge software (gerbmerge?) that i can use as i need to send them one gerber file.
I need to do the following 
 1 gerber file with 0.25" spacing left to right and 0.10" spacing top to bottom in a 14.00"x16" space
Any help would be appreciated