Personal note
MrC work is great, but raises a lot of questions about JRiver's software from earlier on JRiver's strategy revolving 'round it's proprietary own file format. With no "openness" from it into the basic tools so we have to rely on "Third party Programs" written in Perl ? . I can see the consequences today in a distributed Web Environment.
MC provides an amazing array of open APIs to access its database.
Of course the database is proprietary! Even if they used something terrible (with awful performance characteristics for this kind of thing), like MySQL, the "database" itself would still be proprietary because you'd have to deal with its table structure! That would be true of ANY database-driven application of a similar sort.
Sorry, that comment makes absolutely no sense.
MC has a very feature-filled COM API.
MC has a great REST API which you can access with ANY WEB BROWSER or with standard Rest components.
MC writes all tag data you want out to open standards where good ones exist, and to open (and easily machine-readable) XML files for those where it doesn't.
I have no idea what you're referring to, and I suspect you don't either. It is NICE that MrC wrote a scripting system in Perl, but you don't have to use it by any means, and there are a wide variety of powerful ways to access the data inside MC. It is, perhaps, the least locked down powerful media management application I've ever seen (and I've seen a TON of them, which cost WAY more than MC).
About the only places it is lacking where good standard exist is:
* XMP tag writing (which they've made improvements here since last I looked, I think)
* MKV tag writing (for which, unfortunately, there are tagging systems but no standards for tag names or contents, which means no other application would be able to read them anyway).