The proposed amendment seeks to resolve a technical problem. Libraries and schools currently get a rebate. The GST is the federal component of the HST. Until now, the rebate did not apply when books were acquired for resale because, technically speaking, a donation was considered a sale under the legislation because there was a transfer of property. In your example, goods are not acquired by the library for resale. They are acquired in order to be loaned out and to allow people to read the books. If, later on, the library happens to decide to sell the books, they will not be affected. They will be entitled to the rebate because the main purpose was to loan the books.
On May 16th, 2012. See this statement in context.