The Boy Scouts of America has provided long-standing guidelines on permissible fundraising activities for its units. These guidelines are intended to clearly define to the Scouting community and the community at large the role in fundraising of the National Organization, Local Councils and Units. These guidelines are based on the Charter and Bylaws and Rules and Regulations of the Boy Scouts of America and in compliance with IRS regulations related to nonprofit organizations. They are reviewed on a regular basis by committees of the National Executive Board as the fundraising environment is constantly changing.
The Unit Money Earning Application provides a great source for guidance on permissible fundraising activities and is available from your local council or online at this link (PDF).
Additional guidance can be found in a Frequently Asked Questions document available at this link (PDF).
Only the BSA national organization and local councils are authorized to solicit funds in the name of Scouting. Units are permitted to earn money by participating in council-sponsored fundraising activities such as Popcorn sales and Camp Card sales and through the sale of products on their own such as candy bars, Christmas wreaths and trees and other direct sales.
Units can also deliver a service and charge a fee. Examples include a car wash, or a unit that cleaned up after a community festival, conducted by their charter organization, and collected all of the beverage cans and then turned them in for the deposit amount.
In the activity featured on the blog, the unit is providing a service, but as identified by several commenters, by seeking tips are really soliciting a donation, which is not permissible.