Ok, Story time… In the early days of Mondo, i had the honour of hosting RMS at my house for a week and we spoke a lot about this. RMS, Richard Stallman, is the founder of the Free Software Foundation and the GNU project.
When you use Linux, you’re actually using the GNU operating system, with a Linux kernel. Some people prefer to call Linux GNU/Linux. RMS also wrote Emacs, one of the first programmers editors (although i’m a VI man myself…)
Anyway, We spoke lots about Opensource and Freedom and what it would mean for Mondo. Open Source software and Free software overlap, but not totally. Software can be Opensource and Not Free (e.g. Microsoft has opensource software, but you have to agree not to modify it…)
Free software can also be Closed Source… For us, Mondo’s source code IS free software.
We’re free to modify it and use it as we like. Since we’re not asking you to run it on your computer we’re not taking away your freedom.
As pointed out above, opensourcing our core banking system wouldn’t make sense from a business or security stand point, but we will opensource a lot of our core libraries, probably under BSD type licences.
There is one area where we’re not free, that is when we ask you to run closed source, non-free client software on your mobile device. Right now our IOS apps and Android Apps are non-free. I personally feel ok with this. When you buy one of these devices you’re buying into the idea of a closed eco system with enhanced security coming from the strict identification of, and vetting of developers (that’s why it takes us a few days to get an app into the app store…).
Opensourcing our IOS and especially Android clients would also lead to copy-cat apps popping up rapidly that are exact clones, but have money stealing back doors 
By having an open API, we give you the option to bank with us and use only Free software, and i’m sure the community will build many amazing client tools that are free.
Simon