This is significant enough, in and of itself, to be set off in a paragraph. XML is a de facto industry standard from the W3C, and this means that widely deployed, interoperable, industry standard software toolkits can be used to introspect and manipulate the content of XFDL, i.e. Lotus Forms documents, thus mitigating issues of vendor lock-in.
But the story gets better...
The XFDL format internally employs W3C standard XForms, so without further reference to any vendor-specific documents, the standard indicates where in the XFDL document to look for the data content created by an end-user who fills in the Lotus Forms document. Anyone with access to a Java reference manual could write code to prepopulate data into an XFDL (Lotus Forms) document before it is delivered to an end-user, and they can write code to extract data from the document when it is returned to the server for processing.
But the story gets even better...
XFDL incorporates the W3C XML Signatures standard, so widely available industry standard tools are available from multiple vendors for validating the security of digital signatures in XFDL documents. In addition to the Apache XML Security implementation, it is notable that Java itself now natively contains support for XML Signatures (JSR 105).
These standards mean that the entire server-side lifecycle of the Lotus Form can be achieved without being locked into using any particular vendor's API. Any application server, any portal server, any server-side environment that can receive HTTP POSTs and process XML in the POST data can be used in combination with Lotus Forms.
And if you ever hear a vendor try to play up high availability of a client-side browser plugin for processing their favorite file format, ask them "Plugin?? What plugin??" With Lotus Forms, you don't need a browser plugin at all because the Lotus Forms Web Form Server converts the XFDL into dynamic HTML that can be processed directly by the browser with no plugins at all. Best of all, when the user finishes interacting with the Lotus Form, the resulting XFDL document is delivered to the application server endpoint, where it can be processed as XML using the standard APIs.