The .NET business connector allows for integration with AX without BizTalk. The BizTalk Dynamics Adapter actually leverages the .NET business connector. However, it runs independently and does not require BizTalk to be installed.
Install the business connector from the Dynamics AX setup install. You'll see it under the optional components on the AX install screen. You do not need to install the Dynamics AX client or any other Dynamics components in order for it to operate. Take caution that you install the correct version that exactly matches the version of your AX environment; otherwise at runtime you receive a generic error message in your windows event log with no clear indication as to what is wrong.
The business connector acts as a GUI-less client that can be called from a custom .NET assembly. On installation, you'll be prompted for a Dynamics environment that will be used for an initial configuration; this can be changed after installation. As shown...