Applications still running on Server 2003 are unlikely to get updates from developers.
Server 2003 is a dead platform. If not dead, certainly with one foot in the grave or lurching about the countryside looking for brains to consume. Server 2003 is no longer supported by the vendor unless you meet a stringent set of conditions. Most people don’t meet those conditions.
Given that vendors that have living vibrant platforms are having trouble attracting the attention of application developers, it’s reasonable to say that dead (or pining for the fjords) platforms are unlikely to be getting any development love, unless you are in the business of developing malware.
Applications running on Server 2003 are, at best, on life support. It’s hard to thrive in an ecosystem where the life support system has been put out to pasture. The only way to get updated applications is to shift to a platform that isn’t on life support. With some applications, lack of updates won’t matter much. The application does what it needs to do and as long as it keeps doing that, the organization is happy. But that application isn’t going to change and won’t receive any updates. Any faults it has will remain and will never be fixed.