Go to archive.org and search for "Natural Language Understanding James Allen." You can often the scanned PDF for 1 hour or 14 days with a free account. This is 100% legal and supports digital preservation.
A repository called awesome-nlp (starred 15k+ times) sometimes includes links to a scanned copy of the 1995 edition under "Classic Textbooks." Navigate to the README.md and search within for "Allen." natural language understanding james allen pdf github link
How meaning is derived from words and their structural relationships. Go to archive