I don't understand the unexplained downvotes; +1.
What you can do to motivate employees is to allow them to spend a certain amount of their time on researching different platform options, and perhaps to have their own projects they are permitted to work on during work time in a limited manner. This will essentially mean that you pay the same for less of work, so it can be considered to be equivalent to a salary raise. However, the additional motivation will mean you will get part of the effective salary raise back as increased working efficiency.
Who knows, perhaps by allowing them research of different platform options, you will discover some useful library you want for your current platform. Please be careful here, though. Choosing to use an external library isn't a decision to be done lightly. Also, usually a rewrite is considered bad: When is a BIG Rewrite the answer? ...so if using an external library requires a big rewrite, it's usually a bad idea.
Stay away from libraries that call themselves "frameworks". It means you will have to wrap your entire application around such a library, causing major amounts of pain if the framework development is stopped or if you wish to change to yet another framework later. Prefer libraries that affect only limited amount of your code. Do abstract the functionality provided by an external library into a simple wrapper with as simple API as possible; this means if the external library needs to be changed, you will need to rewrite only the simple wrapper, not your entire application.