You may have two different types of money in your beneficiary participant account and each has its own tax advantages.
Traditional (pre-tax) money grows in your account tax-deferred until you withdraw it. However, when you withdraw this money, you have to pay taxes on both the contributions and their earnings (although you will not owe taxes on any tax-exempt contributions in your account).
If you have Roth (after-tax) money in your account, the contributions are tax-free at withdrawal because taxes have already been paid on them. The earnings on those contributions will also be tax-free at withdrawal as long as 5 years have passed since January 1 of the calendar year in which your deceased spouse first made a TSP Roth contribution.
There is no early withdrawal penalty associated with withdrawals from beneficiary participant accounts. However, if you move your beneficiary participant account into your existing civilian or uniformed services TSP account, the early withdrawal penalty rules continue to apply to your existing account.