Although there's no API, NTM does provide two sources of data that I've used. You can export it to Visio (XML syntax) and then you can parse the XML and obtain the data yourself programatically. Another option is to get the data using SQL since NTM stores all the scan data that it obtained in database files located in C:\ProgramData\SolarWinds\Network Topology Mapper\Data (This option seems to have a lot more data than the Visio file). I have made a couple of ruby programs to obtain this information, in case you need something just contact me.
