Thanks, I didn't even see that. The site lists 'free' only for a limited featureset (like 10 requests it seems?). That'll let me check it out at least.
V3 may also be suitable for you as well and is completely free BSD/MIT licensed and is supported by a active community on GitHub. V4 is essentially V3 w/about a years extra work on top. Dennis is the creator of ServiceStack and it is now his full-time job, income supports him in implementing features that corporations - like yours - need.
ps. condolences about the "if it's not from microsoft it doesn't exist", there exists many companies with better cultures. Outliers like you are worth their weight in gold.