Are Richters Seeds Heirloom or Heritage Seeds?

We are interested in heirloom or heritage seeds. Are the seeds found in your catalogue of this kind? Have any been genetically altered?

By "heirloom" or "heritage" seeds you mean traditional varieties that have not been modified by hybridization or genetic engineering. These are open-pollinated, and the seeds collected from them produce progeny similar to the parent. Hybrids do not produce progeny true to the variety.
The vast majority of Richters seeds are either traditional varieties or seeds collected from the wild. Perhaps two or three of the gourmet vegetables are hybrids; otherwise our seeds conform to what is commonly meant by "heirloom" and "heritage" seeds.
Richters was featured in an article in the quarterly magazine put out by Seeds of Diversity organization (formerly, The Heritage Seed Program). Seeds of Diversity is a Canadian non-profit organization seeking to promote and make available heritage seeds to gardeners. Our work to re-introduce and re-popularize herbs from the past was a highlight of the article.

We are looking for Gymnema sylvestre. Do you have any idea where we might find some seeds?

We have not heard of this plant. The name is not a valid latin or botanical plant name. It may be Spanish or Portuguese, but we did not find anything listed under this name in our collection of foreign language herbals.