From the AUS home page:
The API Usage Scanner (AUS) tool can help quickly locate these internal API usages so that compatibility problems can be avoided or remedied. AUS is a pure Java utility that scans Java bytecode for references to targeted APIs. In other words, AUS can be used to scan one product to detect the use of another product's internal APIs. Once these usages are identified, the situation can be remedied by replacing those internal APIs with published ones. If a suitable published API is not available, the product team can alert the API developers of the existence of fragile interfaces between the two products and request an agreement to hold that API stable until a suitable replacement can be provided. Several IBM flagship software products have already done this with great success.What do you think?